Stratum corneum (SC) layer is the most important structure of a skin barrier function and is composed of corneocytes and stratum corneum (SC) intercellular lipid. A multilayer structure of SC intercellular lipid serves to prevent excessive loss of moisture and to suppress penetration of external allergen or hazardous materials into skin. Various kinds of lipids such as sphingolipids, phospholipids, cholesterol sulfate, neutral lipids, etc., are present among corneocytes of the stratum corneum layer. These lipids are present among the corneocytes to function as a skin barrier that prevents moisture evaporation in skin and protects skin from external stimulation or pollution. Ceramide, one of the lipid present in skin, is an N-acylated sphingoid compound, and is a signal transmitter which is involved in cell death. Ceramide synthesis in cells is performed by a complicated biosynthetic pathway of two molecules of serin and palmitoyl-CoA. It has been reported that a total of 11 kinds of ceramides is present in the human stratum corneum layer until now, and in particular, that ceramide 1 plays the most important role in a skin barrier function. Upon observing a structure of the human SC ceramide, a long chain fatty acid having C16 or more is a basic structure. Particularly, the ceramide 1 which is present in the largest content is formed by a combination of omega-hydroxy fatty acid and unsaturated fatty acid. Therefore, in order to synthesize functional pseudo ceramide, it is essential to smoothly supply long chain omega-hydroxy fatty acid.
Natural ceramides that are currently used are extracted mainly from nerve tissues (brain, spinal cord, etc.) of animals, and it is not possible to use the natural ceramides as raw materials for cosmetics due to concerns about safety of mad cow disease (BSE), etc. In addition, a synthetic ceramide is a ceramide produced through a fermentation process using a yeast and a synthesis process, and commercialized synthetic ceramides include ceramide III and ceramide IV. The synthetic ceramides have limitation in being used as a material for cosmetics due to high price of 1.5 to 2 million/kg.
In addition, the ceramide III and the ceramide IV have functional limitations in forming skin barrier and have significantly low solubility to cause problems such as precipitation in formulation, etc., such that it is difficult to use the ceramide III and the ceramide IV at a high concentration.
As compared to general moisturizers, it has been reported that a physiologic lipid mixture including ceramide-based raw materials promotes recovery of a damaged skin barrier function, and in particular, clinical trial results have been published that the physiologic lipid mixture exhibits similar effects to over-average steroids for external use in terms of improving symptoms of atopic dermatitis patients. Despite these advantages, the pseudo ceramide has a disadvantage in that it is difficult to be introduced into various formulations due to high price and low solubility.
In addition, as research has recently focused on a skin barrier function, moisturizers for improving skin barrier using ceramide or pseudo ceramide have been actively developed. Most of the pseudo ceramides that have been developed until now basically have a structure of ceramide III (Korean Patent Publication No. 10-0570553).
Accordingly, the present inventors synthesized a novel pseudo ceramide compound having similar structural characteristics to natural ceramide 1 by using a long chain omega-hydroxy fatty acid, and found that the novel pseudo ceramide compound provides an effect of promoting differentiation of keratinocyte as well as an effect of improving a skin barrier function by using the novel pseudo ceramide compound, and filed the present invention.